1. Field of the Invention
The present invention relates to control apparatuses for vibration type actuators which drive a moving member with multiple degrees of freedom of movement by using at least three different kinds of vibration modes, as well as to such vibration type actuator systems and methods for controlling such a vibration type actuator.
2. Description of Related Art
In the past, numerous vibration type actuators, such as ultrasonic motors, have been proposed. Among these, ultrasonic motors which combine at least three kinds of vibrations to drive a moving member with multiple degrees of freedom, have been proposed.
For example, it has been proposed to form an elliptic motion in a predetermined plane by exciting in a vibration member one longitudinal vibration and two lateral vibrations, and selectively combining two of those three kinds of vibrations, and to drive a moving member contacting the vibration member with multiple degrees of freedom of movement (see for example Japanese Patent Application Laid-open No H11(1999)-164576, pp. 3-4 and FIG. 1).
Furthermore, it has been proposed to regulate the rotation axis of the moving member by regulating the phase difference of AC voltages applied to an ultrasonic motor with the above structure (see for example Japanese Patent Application Laid-open No. H11(1999)-220891, pp. 4-5 and FIG. 1).
Furthermore, it has been proposed to regulate the rotation axis of the moving member by regulating the phase differences and amplitudes of the applied AC voltages (see for example Japanese Patent Application Laid-open No. H11(1999)-220892, pp. 5-13 and FIG. 1).
However, the above-noted conventional technology poses the following problems.
The parameters for controlling the vibration of the vibration type actuator include the driving frequencies, the voltage amplitudes and the phase differences of the applied AC voltages, but in vibration type actuators with multiple degrees of freedom of movement, in which three phases or more AC voltages are applied, there are redundancies or non-linearities in the relation between input and output, and formalization is difficult. As a result, there is the problem that the parameters for performing the desired motion efficiently cannot be determined.